Insulator

ABSTRACT

Provided is an insulator which is capable of reducing an abnormal noise. A first mounting hole engaging a vehicle body side is formed in a first portion, and a second mounting hole engaging an exhaust pipe side is formed in a second portion disposed to be spaced apart from the first portion. The first section and the second portion are coupled to each other by the coupling portion. The first portion and the second portion are adapted such that at least the inner peripheral surfaces of the first mounting hole and the second mounting hole are configured from a rubber-like elastic body having a self-lubrication property.

TECHNICAL FIELD

The present invention relates to an insulator that is made of a rubberelastic body and elastically supports an exhaust pipe, and especiallyrelates to the insulator that can reduce an abnormal noise.

BACKGROUND ART

An insulator made of a rubber elastic body is interposed between avehicle body and an exhaust pipe so as to prevent vibration emitted froma vehicle engine from transmitting to the vehicle body from the exhaustpipe (Patent Literature 1). In the technologies disclosed in PatentLiterature 1, the insulator includes a first portion where a firstmounting hole is formed, a second portion where a second mounting holeis formed, and a pair of coupling portions that connect the firstportion to the second portion. A pin mounted on the vehicle body isinserted into the first mounting hole, and a pin mounted on the exhaustpipe is inserted into the second mounting hole. This consequently causesthe exhaust pipe to be suspended and supported by the vehicle body viathe insulator.

CITATION LIST Patent Literature

[Patent Literature 1] JP-A No. H11-82624

SUMMARY OF INVENTION Technical Problem

However, the above-described conventional technologies have a problemthat arises in that an abnormal noise is caused by the mounting hole andthe second mounting hole rubbing against the pin when the insulatorvibrates due to an exhaust pipe vibration in conjunction with an enginevibration and a vehicle travelling.

The present invention has been made to address the above-describedproblem, and an aim thereof is to provide an insulator that can reducean abnormal noise.

Solution to Problem and Advantageous Effects of Invention

To achieve this object, with an insulator according to claim 1, a firstmounting hole engaging a vehicle body side is formed in a first portion.A second mounting hole engaging an exhaust pipe side is formed in asecond portion and arranged separately from the first portion. Theexhaust pipe is elastically supported by the insulator made of a rubberelastic body. Inner stopper surfaces facing one another inwardly areformed in a pair of coupling portions that connect the first portion tothe second portion. The first portion and the second portionrespectively form a first stopper surface and a second stopper surfacewith a clearance to the inner stopper surface formed in the couplingportion. In the first portion and the second portion, at least innerperipheral surfaces of the first mounting hole and the second mountinghole are made of a rubber elastic body with a self-lubrication property.As a result, the self-lubrication property of the inner peripheralsurfaces of the first mounting hole and the second mounting holeprovides an effect that ensures the reduced abnormal noise made when thefirst mounting hole and the second mounting hole rub against the pin.

With an insulator according to claim 2, the whole made of a rubberelastic body with a self-lubrication property. Here, when a largeexternal force in conjunction with a vehicle travelling is input to theinsulator, the first stopper surface and the second stopper surfacemutually abut, thus ensuring the reduced excessive deformation of theinsulator. In addition to the effect of claim 1, the self-lubricationproperty of the rubber elastic body provides an effect that ensures thereduced abnormal noise made when the first stopper surface and thesecond stopper surface rub.

With an insulator according to claim 3, at least one of the firststopper surface and the second stopper surface opposite to one anotheris formed in a curved surface shape as a part of a cylindrical sidesurface. As a result, the first stopper surface (first portion) or thesecond stopper surface (second portion) formed in the curved surfaceshape as a part of the cylindrical side surface can have a non-linearproperty at the time when abutting and separating. This provides aneffect that allows reducing the abnormal noise made when the stoppersurfaces abut and separate in addition to the effect of claim 1 or 2.

With an insulator according to claim 4, the first stopper surface or thesecond stopper surface formed in the curved surface shape as the part ofthe cylindrical side surface includes a first protrusion that has aprotrusion shape and extends parallel to an axial direction of the firststopper surface or the second stopper surface. The first protrusionprojects toward the facing stopper surface. This ensures the furthernoticeable non-linear property at the time when the first stoppersurface and the second stopper surface abut and separate. This improvesthe effect of reducing the abnormal noise when the stopper surfaces abutor separate in addition to the effect of claim 3.

The first protrusion extends parallel to the axial direction of thefirst stopper surface or the second stopper surface. This provides aneffect that allows obtaining the non-linear property performed by thefirst protrusion also in the case where the first stopper surface andthe second stopper surface are relatively displaced in the axialdirection.

With an insulator according to claim 5, the first stopper surface or thesecond stopper surface formed in the curved surface shape as the part ofthe cylindrical side surface includes a second protrusion that has theprotrusion shape and extends perpendicular to the axial direction of thefirst stopper surface or the second stopper surface. The secondprotrusion projects toward the facing stopper surface. This ensures thefurther noticeable non-linear property at the time when the firststopper surface and the second stopper surface abut and separate. Thisimproves the effect of reducing the abnormal noise when the stoppersurfaces abut or separate in addition to the effect of claim 3 or 4.

The second protrusion extends perpendicular to the axial direction ofthe first stopper surface or the second stopper surface. This providesan effect that allows obtaining the non-linear property performed by thesecond protrusion also in the case where the first stopper surface andthe second stopper surface are relatively displaced in a directionperpendicular to an axis.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a front view of an insulator according to a first embodiment,FIG. 1B is a cross-sectional view of the insulator taken along the lineIb-Ib illustrated in FIG. 1A, and FIG. 1C is a cross-sectional view ofthe insulator taken along the line Ic-Ic illustrated in FIG. 1A.

FIG. 2A is a front view of the insulator according to a secondembodiment, and FIG. 2B is a cross-sectional view of the insulator takenalong the line IIb-IIb illustrated in FIG. 2A.

FIG. 3A is a front view of the insulator according to a thirdembodiment, FIG. 3B is a cross-sectional view of the insulator takenalong the line IIIb-IIIb illustrated in FIG. 3A, and FIG. 3C is across-sectional view of the insulator taken along the line IIIc-IIIcillustrated in FIG. 3A.

FIG. 4A is a front view of the insulator according to a fourthembodiment, FIG. 4B is a cross-sectional view of the insulator takenalong the line IVb-IVb illustrated in FIG. 4A, and FIG. 4C is across-sectional view of the insulator taken along the line IVc-IVcillustrated in FIG. 4A.

FIG. 5A is a front view of the insulator according to a fifthembodiment, FIG. 5B is a cross-sectional view of the insulator takenalong the line Vb-Vb illustrated in FIG. 5A, and FIG. 5C is across-sectional view of the insulator taken along the line Vc-Vcillustrated in FIG. 5A.

FIG. 6A is a front view of the insulator according to a sixthembodiment, FIG. 6B is a cross-sectional view of the insulator takenalong the line VIb-VIb illustrated in FIG. 6A, and FIG. 6C is across-sectional view of the insulator taken along the line VIc-VIcillustrated in FIG. 6A.

FIG. 7A is a front view of the insulator according to a seventhembodiment, FIG. 7B is a cross-sectional view of the insulator takenalong the line VIIb-VIIb illustrated in FIG. 7A, and FIG. 7C is across-sectional view of the insulator taken along the line VIIc-VIIcillustrated in FIG. 7A.

FIG. 8A is a front view of the insulator according to an eighthembodiment, FIG. 8B is a cross-sectional view of the insulator takenalong the line VIIIb-VIIIb illustrated in FIG. 8A, and FIG. 8C is across-sectional view of the insulator taken along the line VIIIc-VIIIcillustrated in FIG. 8A.

FIG. 9A is a front view of the insulator according to a ninthembodiment, FIG. 9B is a cross-sectional view of the insulator takenalong the line IXb-IXb illustrated in FIG. 9A, and FIG. 9C is across-sectional view of the insulator taken along the line IXc-IXcillustrated in FIG. 9A.

FIG. 10A is a front view of the insulator according to a tenthembodiment, FIG. 10B is a cross-sectional view of the insulator takenalong the line Xb-Xb illustrated in FIG. 10A, and FIG. 10C is across-sectional view of the insulator taken along the line Xc-Xcillustrated in FIG. 10A.

FIG. 11A is a front view of the insulator according to a eleventhembodiment, FIG. 11B is a cross-sectional view of the insulator takenalong the line XIb-XIb illustrated in FIG. 11A, and FIG. 11C is across-sectional view of the insulator taken along the line XIc-XIcillustrated in FIG. 11A.

DESCRIPTION OF EMBODIMENT

Preferred embodiments according to the present invention will bedescribed below by referring to the accompanying drawings. A descriptionwill be given of an insulator 1 according to a first embodiment of thepresent invention with reference to FIGS. 1A through 1C. FIG. 1A is afront view of the insulator 1 according to the first embodiment, FIG. 1Bis a cross-sectional view of the insulator 1 taken along the line Ib-Ibillustrated in FIG. 1A, and FIG. 1C is a cross-sectional view of theinsulator 1 taken along the line Ic-Ic illustrated in FIG. 1A.

As illustrated in FIG. 1A to FIG. 1C, the insulator 1 is a member formedin an approximately oval-like shape in a front view, and is integrallymade of a rubber elastic body with a self-lubrication property. As therubber elastic body with the self-lubrication property, the one which alubricant such as fatty acid amide bleeds on the surface of the rubberelastic body to reduce friction coefficient of the surface so as to showlubricity, is employed. Here, insulators 11, 21, 31, 41, 51, 61, 71, 81,91, and 101, which will be described later, are also integrally made ofthe rubber elastic body with the self-lubrication property.

The insulator 1 includes a first portion 2 mounted on a vehicle body(not illustrated) side, a second portion 4 mounted on an exhaust pipe(not illustrated), and a pair of coupling portions 6 that connect thefirst portion 2 to the second portion 4. A first mounting hole 3 havinga circular shape is formed in the first portion 2. A second mountinghole 5 having a circular shape is formed in the second portion 4. A pin(not illustrated) mounted on the vehicle body is inserted into the firstmounting hole 3. A pin (not illustrated) mounted on the exhaust pipethat extends from an engine (not illustrated) is inserted into thesecond mounting hole 5. This consequently causes the exhaust pipe to besuspended and supported by the vehicle body via the insulator 1. Here,the exhaust pipe includes a muffler connected thereto and an exhaust gaspurifying device.

The first portion 2 and the second portion 4 are arranged separatelyfrom one another by the pair of the coupling portions 6 that forms innerstopper surfaces 6 a facing one another inwardly. As a result, a firststopper surface 2 a and a second stopper surface 4 a opposite to oneanother are formed in the first portion and the second portion 4,respectively. The first stopper surface 2 a has a surface formed in aflat surface shape, and intersects orthogonally with a side surface 2 bformed in the flat surface shape. The side surface 2 b faces the flatsurface-shaped inner stopper surface 6 a formed in the coupling portion6 with a clearance.

The second stopper surface 4 a is a surface formed in a curved surfaceshape (semi-cylindrical shape) as a part (approximately halfcircumferential length) of a cylindrical side surface, and has both sideedges continuous with terminal end portions 4 b formed in a recessedsurface shape. The second stopper surface 4 a has the portion near theterminal end portion 4 b (a part of cylindrical side surface) that facesthe flat surface-shaped inner stopper surface 6 a formed in the couplingportion 6 with a clearance.

With the insulator 1, the exhaust pipe (not illustrated) moves up anddown in conjunction with an engine vibration and a vehicle travelling,which causes the first portion 2, the second portion 4, and the couplingportion 6 to expand and contrast in a vertical direction so as to absorbthe vibrations. The first portion 2 and the second portion 4 are made ofthe rubber elastic body with the self-lubrication property. This causesthe first mounting hole 3 and the second mounting hole 5 to include atleast inner peripheral surfaces with the self-lubrication property. As aresult, this ensures the reduced abnormal noise caused by rubbing of thepins (not illustrated) inserted into the first mounting hole 3 and thesecond mounting hole 5 against the inner peripheral surfaces of thefirst mounting hole 3 and the second mounting hole 5.

Applying a large vertical compressive force to the insulator 1 causesthe first stopper surface 2 a and the second stopper surface 4 a to abutone another. Accordingly, excessive deformation of the insulator 1decreases. The second stopper surface 4 a is formed in the curvedsurface shape as the part of the cylindrical side surface. This ensuresthat the first portion 2 and the second portion 4 can have a non-linearproperty when the first stopper surface 2 a and the second stoppersurface 4 a abut one another.

That is, the deformation of the first stopper surface 2 a and the secondstopper surface 4 a gradually increases an area contacting the firststopper surface 2 a along a circumferential direction of the secondstopper surface 4 a (cylindrical side surface). A contact region spreadsfrom a center of the second stopper surface 4 a along thecircumferential direction of the cylindrical side surface. This canprevent air from being contained between the first stopper surface 2 aand the second stopper surface 4 a. As a result, an abnormal noise thatis made when abutting can be reduced.

The first portion 2 and the second portion 4 can have the non-linearproperty, also when the first stopper surface 2 a and the second stoppersurface 4 a which are closely brought into contact separate from oneanother. That is, the deformation of the first stopper surface 2 a andthe second stopper surface 4 a gradually decreases the area contactingthe first stopper surface 2 a along the circumferential direction of thesecond stopper surface 4 a (cylindrical side surface). The contactregion becomes narrower from both sides of the second stopper surface 4a along the circumferential direction of the cylindrical side surface.This ensures the reduced abnormal noise made when separating incomparison with the case of quick separation of both flat surfacesclosely brought into contact from one another.

The second stopper surface 4 a is formed in the curved surface shape asthe part of the cylindrical side surface. This ensures the reducedstress at the time when the first stopper surface 2 a and the secondstopper surface 4 a abut one another (at the time of compressiondeformation) in comparison with a protrusion on which the part of theflat surface is raised. This can prevent fatigue (plastic flow,so-called permanent set) from occurring in comparison with theprotrusion on which the stress is concentrated. The reduction effect ofthe abnormal noise can be ensured over a long period of time.

The first stopper surface 2 a abutting on the second stopper surface 4 ais formed in the flat surface shape, which causes the first stoppersurface 2 a (planar surface) and the second stopper surface 4 a (curvedsurface) to abut one another. The stress can be reduced in comparisonwith the case where both curved surfaces abut one another. This canprevent the first portion 2 and the second portion 4 from becomingfatigued. Therefore, durability of the insulator 1 can be ensured.

The first portion 2 and the second portion 4 have the surfaces (thefirst stopper surface 2 a and the second stopper surface 4 a)constituted of the rubber elastic body with the self-lubricationproperty. This ensures the reduced abnormal noise caused by the mutualrubbing when the first stopper surface 2 a abuts on the second stoppersurface 4 a.

As the exhaust pipe rolls with respect to the vehicle body, the couplingportion 6 bends. Consequently, the first portion 2 and the secondportion 4 are relatively displaced in a lateral direction (theright-left direction in FIG. 1A). This relative displacement causes: theside surface 2 b and the inner stopper surface 6 a; and the secondstopper surface 4 a and the inner stopper surface 6 a to abut oneanother. Accordingly, the excessive deformation of the coupling portion6 decreases. At this time, the second stopper surface 4 a is formed inthe curved surface shape as the part of the cylindrical side surface.This ensures that the second portion 4 and the coupling portion 6 canhave the non-linear property when the second stopper surface 4 a and theinner stopper surface 6 a abut one another.

That is, when the inner stopper surface 6 a and the second stoppersurface 4 a abut one another, the area contacting the inner stoppersurface 6 a along the circumferential direction of the second stagersurface 4 a (cylindrical side surface) gradually increases. The contactregion spreads along the circumferential direction of the cylindricalside surface of the second stopper surface 4 a. This can prevent airfrom being contained between the inner stopper surface 6 a and thesecond stopper surface 4 a. As a result, the abnormal noise made whenabutting can be reduced.

The second portion 4 and the coupling portion 6 may have the non-linearproperty, also when the inner stopper surface 6 a and the second stoppersurface 4 a which are closely brought into contact separate from oneanother. That is, when separating, the area contacting the inner stoppersurface 6 a along the circumferential direction of the second stoppersurface 4 a (cylindrical side surface) gradually decreases. Unlike thecase of the quick separation of both flat surfaces closely brought intocontact from one another, the contact region becomes narrower along thecircumferential direction of the cylindrical side surface of the secondstopper surface 4 a. This ensures that the abnormal noise made whenseparating can be reduced.

The second stopper surface 4 a, which is formed in the curved surfaceshape as the part of the cylindrical side surface, has both side edgescontinuous with the terminal end portions 4 b formed in the recessedsurface shape. Accordingly, the terminal end portion 4 b can have asmaller curvature than that of the terminal end portion where the sidesurface 2 b of the first portion 2 and the inner stopper surface 6 a arecontinuous. As a result, the stress applied to the terminal end portion4 b can be further reduced (dispersed) than that of the terminal endportion of the first portion 2. Therefore, a crack caused by externalforce applied to the insulator 1 can be made hard to occur in theterminal end portion 4 b. As a result, this can increase durability ofthe insulator 1.

The coupling portion 6 has the surface (the inner stopper surface 6 a)constituted of the rubber elastic body with the self-lubricationproperty. This ensures the reduced abnormal noise caused by the mutualrubbing when the inner stopper surface 6 a abuts on the side surface 2b. Similarly, this ensures the reduced abnormal noise caused by themutual rubbing when the inner stopper surface 6 a abuts on the secondstopper surface 4 a.

A description will be given of a second embodiment with reference toFIGS. 2A and 2B. In the second embodiment, the case where a projection12 is formed on the inner stopper surface 6 a will be described. Here,like reference numerals designate corresponding or identical elements inthe first embodiment and the second embodiment, and therefore suchelements will not be further elaborated or simplified here. FIG. 2A is afront view of an insulator 11 according to the second embodiment, andFIG. 2B is a cross-sectional view of the insulator 11 taken along theline IIb-IIb illustrated in FIG. 2A.

As illustrated in FIG. 2A, the insulator 11 forms the plurality ofprojections 12 on a part of the inner stopper surface 6 a facing theside surface 2 b of the first portion 2. The projection 12 is a portionthat projects toward the side surface 2 b of the first portion 2. Asillustrated in FIG. 2B, the projection 12 is disposed over the entirelength of the inner stopper surface 6 a parallel to an axial direction(the right-left direction in FIG. 2B) of the second stopper surface 4 a(a part of cylindrical side surface).

As the exhaust pipe (not illustrated) elastically supported by thevehicle body (not illustrated) employing the insulator 11 rolls, thecoupling portion 6 bends. Consequently, the first portion 2 and thesecond portion 4 are relatively displaced in the lateral direction (theright-left direction in FIG. 2A). This relative displacement causes: theside surface 2 b and the inner stopper surface 6 a; and the secondstopper surface 4 a and the inner stopper surface 6 a to abut oneanother. Accordingly, the excessive deformation of the coupling portion6 decreases. At this time, the projection 12 is disposed on the innerstopper surface 6 a. This ensures that the projection 12 can beinterposed before the side surface 2 b and the inner stopper surface 6 aare closely brought into contact. The side surface 2 b and the innerstopper surface 6 a are closely brought into contact after theprojection 12 is crushed. This can prevent air from being containedbetween the side surface 2 b and the inner stopper surface 6 a (betweenflat surfaces). Therefore, the abnormal noise made when the side surface2 b and the inner stopper surface 6 a abut one another can be reduced.Additionally, the self-lubrication property of the projection 12 and theside surface 2 b ensures the reduced abnormal noise caused by rubbingagainst one another.

As a force in a rotation (yaw) direction around an axis of a vertical(top and bottom in FIG. 2A) is applied to the insulator 11, the couplingportion 6 is twisted around the axis of the vertical. The projection 12is disposed over the entire length of the inner stopper surface 6 a.This ensures that the projection 12 can be interposed before the sidesurface 2 b and the inner stopper surface 6 a are closely brought intocontact. Therefore, the abnormal noise made when the side surface 2 band the inner stopper surface 6 a abut one another can be reduced, alsoin the case where the coupling portion 6 is twisted due to a yawing.

The description has been given of the case where the projection 12 isdisposed on the inner stopper surface 6 a of the coupling portion 6.However, it is not limited to the above, and it is obviously possiblefor a projection to be disposed on the side surface 2 b of the firstportion 2. This also provides similar advantageous effects to those inthe above described embodiment.

A description will be given of a third embodiment with reference toFIGS. 3A through 3C. In the first embodiment and the second embodiment,the description has been given of the case where the first stoppersurface 2 a formed in the first portion 2 is formed in the flat surfaceshape. In contrast, in the third embodiment, a description will be givenof the case where a first stopper surface 22 a formed in a first portion22 is formed in the curved surface shape as the part of the cylindricalside surface. Here, like reference numerals designate corresponding oridentical elements in the first embodiment and the third embodiment, andtherefore such elements will not be further elaborated or simplifiedhere. FIG. 3A is a front view of an insulator 21 according to the thirdembodiment, FIG. 3B is a cross-sectional view of the insulator 21 takenalong the line IIIb-IIIb illustrated in FIG. 3A, and FIG. 3C is across-sectional view of the insulator 21 taken along the line IIIc-IIIcillustrated in FIG. 3A.

Applying a large vertical compressive force to the insulator 21 causesthe first stopper surface 22 a and the second stopper surface 4 a toabut one another. Accordingly, excessive deformation of the insulatordecreases. The first stopper surface 22 a and the second stopper surface4 a are both formed in the curved surface shape (semi-cylindrical shape)as the part (approximately half circumferential length) of thecylindrical side surface. This ensures that the first portion 22 and thesecond portion 4 can have the non-linear property when the first stoppersurface 22 a and the second stopper surface 4 a abut one another.

That is, the deformation of the first stopper surface 22 a and thesecond stopper surface 4 a gradually increases the area closely broughtinto contact to one another along the circumferential direction of thefirst stopper surface 22 a and the second stopper surface 4 a(cylindrical side surface). The contact region spreads from the centerof the first stopper surface 22 a and the second stopper surface 4 aalong the circumferential direction of the cylindrical side surface.This can prevent air from being contained between the first stoppersurface 22 a and the second stopper surface 4 a. The first stoppersurface 22 a and the second stopper surface 4 a are both formed in thecurved surface shape as the part of the cylindrical side surface. Thisimproves the effect of preventing air from being contained in comparisonwith the case where one stopper surface is formed in the flat surfaceshape. As a result, the reduction effect of the abnormal noise made whenabutting can be improved.

When the first stopper surface 22 a and the second stopper surface 4 awhich are closely brought into contact separate from one another, thedeformation of the first stopper surface 22 a and the second stoppersurface 4 a gradually decreases the area closely brought into contact toone another along the circumferential direction of the first stoppersurface 22 a and the second stopper surface 4 a (cylindrical sidesurface). The contact region becomes narrower from both sides of thefirst stopper surface 22 a and the second stopper surface 4 a along thecircumferential direction of the cylindrical side surface. This canimprove the reduction effect of the abnormal noise made when separatingin comparison with the case where one stopper surface is formed in theflat surface shape.

The first stopper surface 22 a is formed in the curved surface shape asthe part of the cylindrical side surface. This ensures that the abnormalnoise made when the inner stopper surface 6 d (flat surface) and thefirst stopper surface 22 a (a part of cylindrical side surface) abut andseparate from one another can be reduced.

The first portion 22 and the second portion 4 have the surfaces (thefirst stopper surface 22 a and the second stopper surface 4 a)constituted of the rubber elastic body with the self-lubricationproperty. This ensures the reduced abnormal noise caused by the mutualrubbing when the first stopper surface 22 a abuts on the second stoppersurface 4 a.

A description will be given of a fourth embodiment with reference toFIGS. 4A through 4C. In the fourth embodiment, the case where aprotrusion (first protrusion 32) is formed on the second stopper surface4 a of the insulator 1 (see FIGS. 1A through 1C) as described in thefirst embodiment will be described. Here, like reference numeralsdesignate corresponding or identical elements in the first embodimentand the fourth embodiment, and therefore such elements will not befurther elaborated or simplified here. FIG. 4A is a front view of aninsulator 31 according to the fourth embodiment, FIG. 4B is across-sectional view of the insulator 31 taken along the line IVb-IVbillustrated in FIG. 4A, and FIG. 4C is a cross-sectional view of theinsulator 31 taken along the line IVc-IVc illustrated in FIG. 4A.

As illustrated in FIG. 4A, the insulator 31 includes the firstprotrusion 32 disposed on the part (top portion) of the second stoppersurface 4 a closest to the first stopper surface 2 a. The firstprotrusion 32 has a cross-sectional shape formed in a semi-cylindricalshape having a larger curvature than that of the second stopper surface4 a. The first protrusion 32, which extends parallel to the axialdirection (the right-left direction in FIG. 4B) of the second stoppersurface 4 a (cylindrical side surface), is formed in a protrusion shapethat projects toward the facing first stopper surface 2 a. The firstprotrusion 32 is disposed approximately over the entire length of thesecond stopper surface 4 a.

Applying a large vertical compressive force to the insulator 31 causesthe first protrusion 32 first to abut on the first stopper surface 2 a.The first stopper surface 22 a and the second stopper surface 4 a areclosely brought into contact after the first protrusion 32 is crushed.The first protrusion 32 has the larger curvature than that of the secondstopper surface 4 a. This can prevent air from being contained betweenthe first stopper surface 2 a and the first protrusion 32 in comparisonwith the case where the first stopper surface 2 a and the second stoppersurface 4 a abut one another. This improves the effect of reducing theabnormal noise made when the first stopper surface 2 a and the secondstopper surface 4 a abut one another.

As a force in a rotation (pitch) direction around an axis of a horizon(right and left in FIG. 4A) is applied to the insulator 31, the couplingportion 6 is twisted around the axis of the horizon. The firstprotrusion 32 is disposed approximately over the entire length of thesecond stopper surface 4 a. This ensures that the first protrusion 32can be interposed before the first stopper surface 2 a and the secondstopper surface 4 a are closely brought into contact. This improves theeffect of reducing the abnormal noise made when the first stoppersurface 2 a and the second stopper surface 4 a abut one another, also inthe case where the coupling portion 6 is twisted due to a pitching.

The first protrusion 32 has the surface constituted of the rubberelastic body with the self-lubrication property. This ensures thereduced abnormal noise caused by the mutual rubbing when the firststopper surface 2 a abuts on the first protrusion 32.

A description will be given of a fifth embodiment with reference toFIGS. 5A through 5C. In the fifth embodiment, the case where theprotrusion (first protrusion 32) is formed on the second stopper surface4 a of the insulator 21 (see FIGS. 3A through 3C) as described in thethird embodiment will be described. Here, like reference numeralsdesignate corresponding or identical elements in the third embodiment,the fourth embodiment, and the fifth embodiment, and therefore suchelements will not be further elaborated or simplified here. FIG. 5A is afront view of an insulator 41 according to the fifth embodiment, FIG. 5Bis a cross-sectional view of the insulator 41 taken along the line Vb-Vbillustrated in FIG. 5A, and FIG. 5C is a cross-sectional view of theinsulator 41 taken along the line Vc-Vc illustrated in FIG. 5A.

As illustrated in FIG. 5A to FIG. 5C, the insulator 41 includes thefirst protrusion 32 disposed on the part (top portion) of the secondstopper surface 4 a closest to the first stopper surface 22 a. Thisprovides similar advantageous effects to those of the insulator 31 asdescribed in the fourth embodiment.

A description will be given of a sixth embodiment with reference toFIGS. 6A through 6C. In the sixth embodiment, the case where aprotrusion (first protrusion 52) is formed on the first stopper surface22 a of the insulator 41 (see FIGS. 5A through 5C) as described in thefifth embodiment will be described. Here, like reference numeralsdesignate corresponding or identical elements in the fifth embodimentand the sixth embodiment and therefore such elements will not be furtherelaborated or simplified here. FIG. 6A is a front view of an insulator51 according to the sixth embodiment, FIG. 6B is a cross-sectional viewof the insulator 51 taken along the line VIb-VIb illustrated in FIG. 6A,and FIG. 6C is a cross-sectional view of the insulator 51 taken alongthe line VIc-VIc illustrated in FIG. 6A.

As illustrated in FIG. 6A, the insulator 51 includes the firstprotrusion 52 disposed on the part (lower portion) of the first stoppersurface 22 a closest to the second stopper surface 4 a. The firstprotrusion 52 has a cross-sectional shape formed in a semi-cylindricalshape having a larger curvature than that of the first stopper surface22 a. The first protrusion 52, which extends parallel to the axialdirection (the right-left direction in FIG. 6B) of the first stoppersurface 22 a (cylindrical side surface), is formed in the protrusionshape that projects toward the facing second stopper surface 4 a. Thefirst protrusion 52, which faces the first protrusion 32 disposed on thesecond stopper surface 4 a, is disposed approximately over the entirelength of the first stopper surface 22 a.

Applying a large vertical compressive force to the insulator 51 causesboth first protrusions 32 and 52 first to abut one another. The firststopper surface 22 a and the second stopper surface 4 a are closelybrought into contact after the first protrusions 32 and 52 are crushed.The first protrusion 52 has the larger curvature than that of the firststopper surface 22 a This can prevent air from being contained betweenthe first protrusions 32 and 52 in comparison with the case where thefirst stopper surface 2 a and the first protrusion 32 abut one another.This improves the effect of reducing the abnormal noise made when thefirst stopper surface 22 a and the second stopper surface 4 a abut oneanother.

The first protrusion 52 has the surface constituted of the rubberelastic body with the self-lubrication property. This ensures thereduced abnormal noise caused by the mutual rubbing when the firstprotrusions 32 and 52 abut one another.

A description will be given of a seventh embodiment with reference toFIGS. 7A through 7C. In the seventh embodiment, the case where aprotrusion (second protrusion 62) is formed on the second stoppersurface 4 a of the insulator 31 (see FIGS. 4A through 4C) as describedin the fourth embodiment will be described. Here, like referencenumerals designate corresponding or identical elements in the fourthembodiment and the seventh embodiment, and therefore such elements willnot be farther elaborated or simplified here. FIG. 7A is a front view ofan insulator 61 according to the seventh embodiment, FIG. 7B is across-sectional view of the insulator 61 taken along the line VIIb-VIIbillustrated in FIG. 7A, and FIG. 7C is a cross-sectional view of theinsulator 61 taken along the line VIIc-VIIc illustrated in FIG. 7A.

As illustrated in FIG. 7A, the insulator 61 includes the secondprotrusion 62, which intersects with the first protrusion 32 disposed onthe second stopper surface 4 a, disposed on the second stopper surface 4a. As illustrated in FIG. 7A and FIG. 7B, a projection height of thesecond protrusion 62 from the second stopper surface 4 a of the portionintersecting with the first protrusion 32 is configured identical to theprojection height of the first protrusion 32. As illustrated in FIG. 7C,the second protrusion 62, which extends perpendicular to the axialdirection (vertical direction in FIG. 7C) of the second stopper surface4 a (cylindrical side surface), is formed in the protrusion shape thatprojects toward the facing first stopper surface 2 a. The secondprotrusion 62 is arranged in the center in the axial direction of thesecond stopper surface 4 a, and disposed approximately over the entirelength of the circumferential direction of the second stopper surface 4a. The projection height of the second protrusion 62 from the secondstopper surface 4 a of both end portions of the circumferentialdirection gradually decreases toward the terminal end portion 4 b. Theprojection height of an end portion of the circumferential direction isset to “0”.

Operation of the insulator 61 performed when the large verticalcompressive force being applied is similar to those of the insulator 31according to the fourth embodiment, and therefore will not be furtherdescribed. With this the insulator 61, similar advantageous effects tothose of the insulator 31 according to the fourth embodiment can beprovided.

As a force in a rotation (roll) direction around an axis in front andrear (vertical with respect to paper surface in FIG. 7A) is applied tothe insulator 61, the coupling portion 6 is twisted around the axis infront and rear. The second protrusion 62 is disposed approximately overthe entire length of the circumferential direction of the second stoppersurface 4 a. This ensures that the second protrusion 62 can beinterposed before the first stopper surface 2 a and the second stoppersurface 4 a are closely brought into contact. This improves the effectof reducing the abnormal noise made when the first stopper surface 2 aand the second stopper surface 4 a abut one another, also in the casewhere the coupling portion 6 is twisted due to a rolling.

The projection height of the second protrusion 62 from the secondstopper surface 4 a of both end portions of the circumferentialdirection gradually decreases toward the terminal end portion 4 b. Theprojection height of the end portion of the circumferential direction isset to “0”. As a result, when the exhaust, pipe rolls with respect tothe vehicle body and causes the second stopper surface 4 a and the innerstopper surface 6 a to abut one another, a load can be prevented frombeing applied to the second protrusion 62 (especially end portion of thecircumferential direction). This can prevent the second protrusion 62from being subjected to a plastic flow fatigue, and accordingly canprolong the life of the second protrusion 62.

The second protrusion 62 has the surface constituted of the rubberelastic body with the self-lubrication property. This ensures thereduced abnormal noise caused by the mutual rubbing when the firststopper surface 2 a abuts on the second protrusion 62.

A description will be given of an eighth embodiment with reference toFIGS. 8A through 8C. In the eighth embodiment, the case where a secondprotrusion 72 is formed, instead of the second protrusion 62 formed onthe second stopper surface 4 a of the insulator 61 (see FIGS. 7A through7C) as described in the seventh embodiment, will be described. Here,like reference numerals designate corresponding or identical elements inthe fourth embodiment and the eighth embodiment, and therefore suchelements will not be further elaborated or simplified here. FIG. 8A is afront view of an insulator 71 according to the eighth embodiment, FIG.8B is a cross-sectional view of the insulator 71 taken along the lineVIIIb-VIIIb illustrated in FIG. 8A, and FIG. 8C is a cross-sectionalview of the insulator 71 taken along the line VIIIc-VIIIc illustrated inFIG. 8A.

As illustrated in FIG. 8A, the insulator 71 includes the secondprotrusion 72, which intersects with the first protrusion 32 disposed onthe second stopper surface 4 a, disposed on the second stopper surface 4a. As illustrated in FIG. 8A and FIG. 8B, a projection height of thesecond protrusion 72 from the second stopper surface 4 a of the portionintersecting with the first protrusion 32 is configured identical to theprojection height of the first protrusion 32. As illustrated in FIG. 8C,the second protrusion 72, which extends perpendicular to the axialdirection (vertical direction in FIG. 8C) of the second stopper surface4 a (cylindrical side surface), is formed in the protrusion shape thatprojects toward the facing first stopper surface 2 a. The secondprotrusion 72 is arranged in the center in the axial direction of thesecond stopper surface 4 a, and disposed approximately over the entirelength of the circumferential direction of the second stopper surface 4a. The second protrusion 72 includes an end portion 72 a of both sidesof the circumferential direction which projects from the second stoppersurface 4 a toward the inner stopper surface 6 a.

The operations of the insulator 71 performed when the large verticalcompressive force and the force in the rotation (roll) direction beingapplied are similar to those of the insulator 61 according to theseventh embodiment, and therefore will not be further described. Withthis the insulator 71, similar advantageous effects to those of theinsulator 61 according to the seventh embodiment can be provided.

The second protrusion 72 includes the end portion 72 a of both sides ofthe circumferential direction that projects from the second stoppersurface 4 a toward the inner stopper surface 6 a. As a result, when theexhaust pipe rolls with respect to the vehicle body and causes thesecond stopper surface 4 a and the inner stopper surface 6 a to abut oneanother, the end portion 72 a can be interposed before the secondstopper surface 4 a and the inner stopper surface 6 a are closelybrought into contact. The second stopper surface 4 a and the innerstopper surface 6 a are closely brought into contact after the endportion 72 a is crushed. This can prevent air from being containedbetween the second stopper surface 4 a (cylindrical side surface) andthe inner stopper surface 6 a (between flat surfaces). This improves theeffect of reducing the abnormal noise made when the second stoppersurface 4 a and the inner stopper surface 6 a abut one another.

The second protrusion 72 has the surface constituted of the rubberelastic body with the self-lubrication property. This ensures thereduced abnormal noise caused by the mutual rubbing when the firststopper surface 2 a abuts on the second protrusion 72, or when the innerstopper surface 6 a abuts on the second protrusion 72 (the end portion72 a).

A description will be given of a ninth embodiment with reference toFIGS. 9A through 9C. In the ninth embodiment, the case where theprotrusion (second protrusion 62) is formed on the second stoppersurface 4 a of the insulator 41 (see FIGS. 5A through 5C) as describedin the fifth embodiment will be described. Here, like reference numeralsdesignate corresponding or identical elements in the fifth embodiment,the seventh embodiment, and the ninth embodiment, and therefore suchelements will not be further elaborated or simplified here. FIG. 9A is afront view of an insulator 81 according to the ninth embodiment, FIG. 9Bis a cross-sectional view of the insulator 81 taken along the lineIXb-IXb illustrated in FIG. 9A, and FIG. 9C is a cross-sectional view ofthe insulator 81 taken along the line IXc-IXc illustrated in FIG. 9A.

As illustrated in FIG. 9A to FIG. 9C, the insulator 81 includes thesecond protrusion 62, which intersects with the first protrusion 32disposed on the second stopper surface 4 a, disposed on the secondstopper surface 4 a. This provides similar advantageous effects to thoseof the insulator 61 as described in the seventh embodiment.

A description will be given of a tenth embodiment with reference toFIGS. 10A through 10C. In the tenth embodiment, the case where theprotrusions (first protrusion 52 and second protrusion 92) are formed onthe first stopper surface 22 a of the insulator 81 (see FIGS. 9A through9C) as described in the ninth embodiment will be described. Here, likereference numerals designate corresponding or identical elements in thesixth embodiment, the seventh embodiment, and the tenth embodiment, andtherefore such elements will not be further elaborated or simplifiedhere. FIG. 10A is a front view of an insulator 91 according to the tenthembodiment, FIG. 10B is a cross-sectional view of the insulator 91 takenalong the line Xb-Xb illustrated in FIG. 10A, and FIG. 10C is across-sectional view of the insulator 91 taken along the line Xc-Xcillustrated in FIG. 10A.

As illustrated in FIG. 10A, the insulator 91 includes the firstprotrusion 52 disposed on the part of the first stopper surface 22 aclosest to the second stopper surface 4 a. The first protrusion 52 hasthe cross-sectional shape formed in the semi-cylindrical shape havingthe larger curvature than that of the first stopper surface 22 a. Thefirst protrusion 52, which extends parallel to the axial direction (theright-left direction in FIG. 10B) of the first stopper surface 22 a(cylindrical side surface), is formed in the protrusion shape thatprojects toward the facing second stopper surface 4 a. The firstprotrusion 52, which faces the first protrusion 32 disposed on thesecond stopper surface 4 a, is disposed approximately over the entirelength of the first stopper surface 22 a.

The insulator 91 includes the second protrusion 92, which intersectswith the first protrusion 52, disposed on the first stopper surface 22a. As illustrated in FIG. 10A and FIG. 10B, a projection height of thesecond protrusion 92 from the first stopper surface 22 a of the portionintersecting with the first protrusion 52 is configured identical to theprojection height of the first protrusion 52. The second protrusion 92,which extends perpendicular to the axial direction (vertical directionwith respect to paper surface in FIG. 10A) of the first stopper surface22 a (cylindrical side surface), is formed in the protrusion shape thatprojects toward the facing second stopper surface 4 a. The secondprotrusion 92 is arranged in the center in the axial direction of thefirst stopper surface 22 a. The second protrusion 92, which faces thesecond protrusion 62 disposed on the second stopper surface 4 a, isdisposed approximately over the entire length of the circumferentialdirection of the first stopper surface 22 a. The projection height ofthe second protrusion 92 from the first stopper surface 22 a of both endportions of the circumferential direction gradually decreases toward aterminal end portion 22 b. The projection height of the end portion ofthe circumferential direction is set to “0”.

As a large compressive force in the roll direction is applied to theinsulator 91, the coupling portion 6 is twisted around the axis in frontand rear (vertical with respect to paper surface in FIG. 10A). Thesecond protrusions 62 and 92 are disposed approximately over the entirelength of the circumferential direction of the first stopper surface 22a and the second stopper surface 4 a, respectively. This ensures thatthe second protrusions 62 and 92 can be interposed before the firststopper surface 22 a and the second stopper surface 4 a are closelybrought into contact. This improves the effect of reducing the abnormalnoise made when the first stopper surface 22 a and the second stoppersurface 4 a abut one another, also in the case where the couplingportion 6 is twisted due to the rolling.

The second protrusion 92 has the surface constituted of the rubberelastic body with the self-lubrication property. This ensures thereduced abnormal noise caused by the mutual rubbing when the secondstopper surface 4 a abuts on the second protrusion 92, or when thesecond protrusions 62 and 92 abut one another.

A description will be given of an eleventh embodiment with reference toFIGS. 11A through 11C. In the first to the tenth embodiments, thedescription has been given of the case where at least one of the firststopper surface 2 a or 22 a and the second stopper surface 4 a is formedin a curved surface shape as a part of a cylindrical side surface. Incontrast to this, in the eleventh embodiment, a description will begiven of the case where both a first stopper surface 2 a and a secondstopper surface 102 a are formed in the flat surface shape. Here, likereference numerals designate corresponding or identical elementsdescribed in the first embodiment, and therefore such elements will notbe further elaborated or simplified here. FIG. 11A is a front view ofthe insulator 101 according to a eleventh embodiment, FIG. 11B is across-sectional view of the insulator 101 taken along the line XIb-XIbillustrated in FIG. 11A is a cross-sectional view of the insulator 101taken along the line XIc-XIc illustrated in FIG. 11A.

The insulator 101 includes a first, portion 2 and a second portion 102connected by a pair of coupling portions 6. In the second portion 102,the second stopper surface 102 a is formed opposed to the first stoppersurface 2 a. The second stopper surface 102 a has a surface formed in aflat surface shape, and intersects orthogonally with a side surface 102b formed in a flat surface shape. The side surface 102 b is opposed witha clearance to a flat surface-shaped inner stopper surface 6 a formed inthe coupling portion 6.

With the insulator 101, the first portion 2 and the second portion 102are made of the rubber elastic body with the self-lubrication property.This ensures the reduced abnormal noise caused by rubbing of pins (notillustrated) inserted into a first mounting hole 3 and a second mountinghole 5 against inner peripheral surfaces of the first mounting hole 3and the second mounting hole 5, respectively.

The first portion 2 and the second portion 102 have the surfaces (thefirst stopper surface 2 a and the second stopper surface 102 a)constituted of the rubber elastic body with the self-lubricationproperty. This ensures the reduced abnormal noise caused by the mutualrubbing when the first stopper surface 2 a abuts on the second stoppersurface 102 a. Furthermore, the coupling portions 6 has the surface (theinner stopper surface 6 a) constituted of the rubber elastic body withthe self-lubrication property. This ensures the reduced abnormal noisecaused by the mutual rubbing when the inner stopper surface 6 a abuts onthe side surfaces 2 b and 102 b.

As described above, the present invention has been described based onthe above-mentioned embodiments. It will be appreciated that the presentinvention will not be limited to the embodiments described above, butvarious modifications are possible without departing from the technicalscope of the present invention. For example, the shapes of the whole andeach portion of the insulators 1, 11, 21, 31, 41, 51, 61, 71, 81, 91,and 101, and such as shape and quantity of the projection 12 may beconfigured appropriately.

In the above-described respective embodiments, the description has beengiven of the cases where the whole shape of the insulators 1, 11, 21,31, 41, 51, 61, 71, 81, 91, and 101 is formed in the approximatelyoval-like shape in the front view. This, however, should not beconstrued in a limiting sense. It is obviously possible to form thewhole shape of the insulators in a well-known shape such as anapproximately circular shape, a cornered rectangular shape, anapproximately semicircular shape in the front view.

In the above-described respective embodiments, the description has beengiven of the cases where one of the circular-shaped first mounting hole3 and the second mounting hole 5 are formed in each of the firstportions 2 and 22, and the second portion 4 and 102, respectively. This,however, should not be construed in a limiting sense. It is obviouslypossible for the shape and the quantity of the first mounting hole 3 andthe second mounting hole 5 to be configured appropriately correspondingto the shape and the quantity of a bracket and a pin mounted in thevehicle body and the exhaust pipe.

In the above-described respective embodiments, the description has beengiven of the cases where the pair of the coupling portions 6 is formedin a tabular shape so as to linearly extend in the vertical direction.However, it is not limited to the above, and it is obviously possiblefor the coupling portion 6 to be formed in a curved plate shape.

In the first to the tenth embodiments, the description has been given ofthe cases where the second stopper surface 4 a of the second portion 4is always formed in the curved surface shape as the part of thecylindrical side surface. This, however, should not be construed in alimiting sense. It is obviously possible to form the first stoppersurface 22 a of the first portion 22 in the curved surface shape as thepart of the cylindrical side surface, and to form the second stoppersurface of the second portion in the various shapes such as flatsurface. Also, in this case the first stopper surface 22 a of the firstportion 22 is formed in the curved surface shape as the part of thecylindrical side surface, and accordingly it is possible to prevent theabnormal noise made when the first stopper surface and the secondstopper surface abut and separate from one another while the largevertical compressive force is applied to the insulator.

In the first to the tenth embodiments, the description has been given ofthe cases where the first protrusions 32 and 52 intersecting with thesecond protrusions 62, 72, and 92 are always disposed when disposing thesecond protrusions 62, 72, and 92. This, however, should not beconstrued in a limiting sense. It is obviously possible for the secondprotrusions 62, 72, and 92 without the first protrusions 32 and 52 to bedisposed. Disposing the second protrusions 62, 72, and 92 improves theeffect of reducing the abnormal noise when the large compressive forcein the roll direction is applied to the insulator.

In the second embodiment, the description has been given of the caseswhere the projection 12 is disposed on the inner stopper surface 6 athan faces the side surface 2 b of the first portion 2 formed in theflat surface shape. This, however, should not be construed in a limitingsense. It is obviously possible for the projection 12 to be disposed onthe inner stopper surface 6 a that faces the second stopper surface 4 aformed in the curved surface shape as the part of the cylindrical sidesurface. The projection 12 can improve the effect of reducing theabnormal noise made when the second stopper surface 4 a (cylindricalside surface) and the inner stopper surface 6 a abut one another.

In the above-described embodiments, while the description is omitted,the insulators 1, 11, 21, 31, 41, 51, 61, 71, 81, 91 and 101 may beproduced by different material molding (Method of integrating aplurality of kinds of materials by adhesion in a forming process). Forexample, the first stopper surfaces 2 a and 22 a (first portions 2, 22)and the second stopper surface 4 a (second portion 4) are made ofdifferent material. This enhances the effect of reducing the abnormalnoise made when the first stopper surfaces 2 a and 22 a abut on thesecond stopper surface 4 a.

In the above-described respective embodiments, the description has beengiven of the cases where the insulators 1, 11, 21, 31, 41, 51, 61, 71,81, 91, and 101 are integrally made of the rubber elastic body with theself-lubrication property. This, however, should not be construed in alimiting sense. It is obviously possible that the first mounting hole 3and the second mounting hole 5 include inner peripheral surfaces andtheir peripheral areas formed in a rubber elastic body with theself-lubrication property by the different material molding. Thisensures the reduced abnormal noise caused by rubbing of the pins (notillustrated) inserted into the first mounting hole 3 and the secondmounting hole 5 against the inner peripheral surfaces of the firstmounting hole 3 and the second mounting hole 5.

Furthermore, it is obviously possible that the first portions 2 and 22and the second portions 4 and 102 are formed in a rubber elastic bodywith the self-lubrication property by the different material molding.This ensures the reduced abnormal noise caused by the rubbing when thefirst stopper surface 2 a or 22 a and the second stopper surface 4 a or102 a abut on one another in addition to ensuring the reduced abnormalnoise caused by rubbing of the pins (not illustrated) inserted into thefirst mounting hole 3 and the second mounting hole 5 against the innerperipheral surfaces of the first mounting hole 3 and the second mountinghole 5.

The invention claimed is:
 1. An insulator made of a rubber elastic bodyand elastically supporting an exhaust pipe, the insulator comprising: afirst portion that includes a formed first mounting hole, the firstmounting hole engaging a vehicle body side; a second portion arrangedseparately from the first portion, the second portion including a formedsecond mounting hole, the second mounting hole engaging the exhaust pipeside; a pair of coupling portions that connects the second portion tothe first portion, the pair of the coupling portions including formedinner stopper surfaces, the inner stopper surfaces facing one anotherinwardly; and a first stopper surface and a second stopper surface thatare respectively formed in the first portion and the second portion witha clearance to the inner stopper surfaces of the pair of the couplingportions, the first stopper surface and the second stopper surface beingopposite to one another, wherein the first portion and the secondportion include at least inner peripheral surfaces of the first mountinghole and the second mounting hole, the inner peripheral surfaces beingmade of a rubber elastic body with a self-lubrication property, whereinone of the first or second stopper surfaces includes a singleaxially-extending curved abutting portion that contacts the other of thefirst or the second stopper surfaces when an external force deforms theinsulator such that the first and second stopper surfaces initiallyabut, said single axially-extending curved abutting surface of said oneof the first or second stopper surfaces having a greater degree ofcurvature than an initial abutment surface of the other of the first orsecond stopper surfaces at a contact point where the first and secondstopper surfaces initially abut, wherein at least one of the firststopper surface and the second stopper surface is formed in a curvedsurface shape as a part of a cylindrical side surface, and wherein thefirst stopper surface or the second stopper surface formed in the curvedsurface shape as the part of the cylindrical side surface includes asecond protrusion having a protrusion shape, the second protrusionextending perpendicular to an axial direction of the first stoppersurface or the second stopper surface, the second protrusion projectingtoward the facing stopper surface.
 2. The insulator according to claim1, wherein an entirety of the rubber elastic body is made with aself-lubrication property.
 3. The insulator according to claim 2,wherein said single axially-extending curved abutting portion includesthat at least one of the first stopper surface and the second stoppersurface is formed in a curved surface shape as a part of a cylindricalside surface.
 4. The insulator according to claim 2, wherein at leastone of the first stopper surface and the second stopper surface isformed in a curved surface shape as a part of a cylindrical sidesurface, and wherein the first stopper surface or the second stoppersurface formed in the curved surface shape as the part of thecylindrical side surface includes a first protrusion having a protrusionshape that forms said single axially-extending curved abutting portion,the first protrusion extending parallel to an axial direction of thefirst stopper surface or the second stopper surface, the firstprotrusion projecting toward the facing stopper surface.
 5. Theinsulator according to claim 1, wherein said single axially-extendingcurved abutting portion includes that at least one of the first stoppersurface and the second stopper surface is formed in a curved surfaceshape as a part of a cylindrical side surface.
 6. The insulatoraccording to claim 1, wherein at least one of the first stopper surfaceand the second stopper surface is formed in a curved surface shape as apart of a cylindrical side surface, and wherein the first stoppersurface or the second stopper surface formed in the curved surface shapeas the part of the cylindrical side surface includes a first protrusionhaving a protrusion shape that forms said single axially-extendingcurved abutting portion, the first protrusion extending parallel to anaxial direction of the first stopper surface or the second stoppersurface, the first protrusion projecting toward the facing stoppersurface.
 7. The insulator according to claim 6, wherein the firststopper surface or the second stopper surface formed in the curvedsurface shape as the part of the cylindrical side surface includes asecond protrusion having a protrusion shape, the second protrusionextending perpendicular to an axial direction of the first stoppersurface or the second stopper surface, the second protrusion projectingtoward the facing stopper surface.